AI & TechnologyFCM Legacy API Shutdown: Fixing Push and the 2027 Deadline

If your app's push notifications stopped arriving in mid-2024, your server was probably still using the legacy FCM API, which Firebase began shutting down on July 22, 2024. The fix is on the server: send through the FCM HTTP v1 API, ideally with the Firebase Admin SDK, and replace the old server key with a service account. Then check the second deadline: the InstanceId server APIs and device groups stop working after September 29, 2027.

If you landed here from a tutorial that links to Firebase's old migration guide, that page now returns 404. The dates and steps here come from Firebase's own documentation, as listed in the sources, including an archived copy of that guide. I tested the old endpoint and guide URL myself on October 18, 2026.

Disclosure: App369 is my studio. I build and fix Flutter and Firebase apps for a living, including push notifications, and the last section mentions what I sell. Google doesn't pay me for anything on this page.

What changed, and when

Firebase says there is no service downgrade before September 29, 2027, so the second change gives you roughly a year from the announcement. The first one is already done.

What the old addresses do today

Checked on October 18, 2026:

• A POST to https://fcm.googleapis.com/fcm/send, the legacy send endpoint, returned 404.
• firebase.google.com/docs/cloud-messaging/migrate-v1, the migration guide most tutorials link to, returned 404. The Wayback Machine copy from January 2026 still has the full text.
• firebase.google.com/docs/cloud-messaging/http-server-ref, the legacy protocol reference, redirects to Firebase's server environment page.

Moving sends to HTTP v1

1. Find the old code. Search your server, Cloud Functions and any scripts for fcm.googleapis.com/fcm/send, an Authorization: key= header, registration_ids, or an XMPP connection to FCM. Also check third-party tools or plugins that send pushes for you: any that were set up with an FCM server key need updating or replacing.
2. Use the Admin SDK if you can. Firebase calls the Admin SDK the recommended method for sending from a server. It handles authorization and the new message format, and it can send the same message to a list of tokens for you.
3. Or call HTTP v1 directly. Send a POST to https://fcm.googleapis.com/v1/projects/PROJECT_ID/messages:send with an Authorization: Bearer <access token> header. The token is a short-lived OAuth 2.0 access token from a service account, requested with the https://www.googleapis.com/auth/firebase.messaging scope. Google's auth libraries can request and refresh it.
4. Change the message shape. HTTP v1 wraps everything in a message object with exactly one target, such as a token, a topic or a condition. Platform settings move into android, apns and webpush blocks. There's no registration_ids list. To reach many devices, send one request per token, use a topic or condition, or use the Admin SDK's multi-token sending, which still makes one request per token behind the scenes.
5. Enable the API. If you get errors reaching the endpoint, check that "Firebase Cloud Messaging API" is enabled for the project in the Google Cloud console, as Firebase's guide says.
6. Keep the service account key off devices. It belongs on your server or in a secret manager, never in the mobile app or a public repository. If a key was ever committed to a repository, replace it.
7. Test with real devices. Send a test message to an Android phone and an iPhone (and a web client, if you use FCM on the web), with the app in the foreground, in the background and closed, before you remove the old code path. Once nothing uses them, delete or restrict the old server keys so they can't be leaked and reused.

Before September 29, 2027

The second deprecation hits apps that used the older InstanceId server APIs or device groups, even if sending already moved to HTTP v1.

If you manage topic subscriptions with the Firebase Admin SDK, Firebase says earlier versions are affected and lists the versions to upgrade to: Node.js 14.5.0 or later, Python 7.7.0 or later, Java 9.11.0 or later, Go 4.22.0 or later, and .NET 3.7.0 or later.

Need a hand?

If pushes still don't arrive after the move, or you're not sure which parts of your backend touch the old APIs, the App Fix Ticket covers API, webhook and Cloud Function errors in two fixed-price steps. A $450 Diagnosis gives you the root cause with evidence and a fixed repair quote within 3 business days, credited toward the fix. If you go ahead, the $1,200 Fix takes 5 business days. For help with something else in a Firebase app, see how to debug a Flutter and Firebase bug, or send me a short description.